What Is Windows Communication Foundation?
Windows Communication
Foundation (WCF) is a framework for building service-oriented applications.
In Development phases Microsoft code named WCF as Indigo. Service-oriented applications are applications build using
service oriented architecture (SOA) principle
Service-oriented architecture
(SOA) is the reliance on Web services to send and receive data. The services have the general advantage of
being loosely-coupled instead of hard-coded from one application to
another. A loosely-coupled relationship implies that any client created on any platform can connect to any service as long
as the essential contracts are met.
Using WCF, one can send data as asynchronous messages from one
service endpoint to another data can be
binary data or Word send as XML.WCF service can be hosted in IIS or in an
application e.g. a console application or web application.
WCF unifies the programming model provided in .Net Framework;
WCF combines features of Web Service, Remoting, MSMQ and COM+. WCF & provides
a common platform for all .NET communication.
Where WCF can be used
?
When we
need
· A secure service to process business transactions.
· A service that supplies current data to others, such as a
traffic report or other monitoring service.
· A chat service that allows two people to communicate or
exchange data in real time.
· A dashboard application that polls one or more services for
data and presents it in a logical presentation.
· Exposing a workflow implemented using Windows Workflow
Foundation as a WCF service.
· A Silverlight application to poll a service for the latest
data feeds.
Features of WCF
· Service
Orientation
WCF enables us to create service oriented applications.
WCF enables us to create service oriented applications.
· Interoperability
1) WCF can be used to extend existing
legacy code in COM+ rather than
having to rewrite it.
2) WCF allows COM developer consume WCF Service using service
moniker.
3) .NET Remoting
applications integration and migration- .Net Remoting 2.0 and WCF can be
side by side, letting us to expose the same business objects over both
technologies simultaneously without having to modify our existing .Net Remoting
2.0 code. One can migrate entire service to WCF. Migration from .NET Remoting
2.0 to WCF requires changes to the remote object's interface and its configuration
settings.
Remoting needs
client & server both developed on .Net unlike Web service or WCF. In
remoting, both applications know about each other. A proxy of an application
object is created on the other application.
A recent comparison of WCF & Remoting using performance counters
has proven that WCF has an edge over predecessor.
4) Interoperability
between ASP.NET Web services & WCF: Interoperability can be achieved by
ensuring that services implemented using both technologies conform to the WS-I Basic Profile 1.1 specification.
ASP.NET Web services that conform to WS-I
Basic Profile 1.1 are interoperable with WCF clients by using WCF
system-provided binding BasicHttpBinding
5) “Plain Old XML” (POX) applications
communicate by exchanging raw HTTP messages that contain only XML application
data that is not enclosed within a SOAP envelope.
WCF can be used to
implement services that expose endpoints to clients such as Web browsers and
scripting languages that send and receive POX messages. WCF programming model
can be used to implement clients that communicate with POX-based services.
· Multiple
Message Patterns
WCF let us to implement services that can exchange messages in several well-known patterns.
WCF let us to implement services that can exchange messages in several well-known patterns.
Request/Reply pattern: The most common
pattern is the request/reply pattern,
where one endpoint requests data from a second endpoint. The second endpoint
replies.
One-Way Message: A
one-way message in which a single
endpoint sends a message without any expectation of a reply.
Duplex exchange pattern:
In the duplex exchange pattern , two
endpoints establish a connection and send data back and forth, similar to an
instant messaging program.
· Service
Metadata
WCF supports publishing service metadata using formats specified in industry standards such as WSDL, XML Schema and WS-Policy. This metadata can be used to automatically generate and configure clients for accessing WCF services. Metadata can be published over HTTP and HTTPS or using the Web Service Metadata Exchange standard
WCF supports publishing service metadata using formats specified in industry standards such as WSDL, XML Schema and WS-Policy. This metadata can be used to automatically generate and configure clients for accessing WCF services. Metadata can be published over HTTP and HTTPS or using the Web Service Metadata Exchange standard
· Data Contracts
A data contract is a formal agreement between a service and a client that abstractly describes the data to be exchanged. That is, to communicate, the client and the service do not have to share the same types, only the same data contracts. A data contract precisely defines, for each parameter or return type, what data is serialized (turned into XML) to be exchanged.
A data contract is a formal agreement between a service and a client that abstractly describes the data to be exchanged. That is, to communicate, the client and the service do not have to share the same types, only the same data contracts. A data contract precisely defines, for each parameter or return type, what data is serialized (turned into XML) to be exchanged.
The easiest way to handle data
is by creating classes that represent a data entity with properties that belong
to the data entity.
WCF includes a comprehensive system for
working with data in this easy manner. Once
you have created the classes that represent data, your service automatically
generates the metadata that allows clients to comply with the data types you
have designed.
· Security
Messages can be encrypted to protect privacy and you can require users to authenticate themselves before being allowed to receive messages. Security can be implemented using well-known standards such as SSL or WS-SecureConversation.
Messages can be encrypted to protect privacy and you can require users to authenticate themselves before being allowed to receive messages. Security can be implemented using well-known standards such as SSL or WS-SecureConversation.
· Multiple
Transports and Encodings
Messages can be sent on any of several built-in transport protocols and encodings. The most common protocol and encoding is to send text encoded SOAP messages using is the HyperText Transfer Protocol (HTTP) for use on the World Wide Web.
Messages can be sent on any of several built-in transport protocols and encodings. The most common protocol and encoding is to send text encoded SOAP messages using is the HyperText Transfer Protocol (HTTP) for use on the World Wide Web.
Alternatively, WCF allows us to send
messages over TCP, named pipes, or MSMQ.
These messages can be encoded as text or using an optimized binary format. Binary data can be sent efficiently using
the MTOM standard. If none of the provided transports or encodings suit
your needs you can create your own
custom transport or encoding.
· Reliable
and Queued Messages
WCF supports reliable message exchange using reliable sessions implemented over WS-Reliable Messaging and using MSMQ.
WCF supports reliable message exchange using reliable sessions implemented over WS-Reliable Messaging and using MSMQ.
Reliable messaging is how a reliable
messaging source (called the source) transfers messages reliably to a reliable
messaging destination (called the destination).
Reliable messaging has the following
key aspects:
- Transfer assurances for messages sent from a source to a destination regardless of message transfer failure or transport failures.
- Separation of the source and the destination from each other, which provides independent failure and recovery of the source and the destination as well as reliable transfer and delivery of messages even though the source or destination is unavailable.
1)
Reliable Session:
Reliable sessions provide end-to-end reliable transfer of messages between a
source and a destination using the WS-ReliableMessaging
protocol regardless of the number or type of intermediaries that separate the
messaging (source and destination) endpoints. It Includes transport intermediaries that uses SOAP or
Not using SOAP.
The reliable session WCF ensures
that messages sent between endpoints are transferred across SOAP or transport
intermediaries and are delivered only once and, optionally, in the same order
in which they were sent.
It offer reliable transfer
without the cost of high latency
2)
Queues
in WCF: WCF queued
communication is built on top of Message Queuing (also known as MSMQ). WCF
queued communication is built on top of Message Queuing (also known as MSMQ).
MSMQ
is shipped as an option with Windows that runs as an NT service.
It captures messages for transmission in a transmission queue on behalf of the
source and delivers it to a target queue. The target queue accepts messages on
behalf of the destination for later delivery whenever the destination requests
for messages.
The MSMQ queue managers implement a reliable message-transfer protocol so
that messages are not lost in transmission. The protocol can be native or
SOAP-based, such as Soap Reliable
Messaging Protocol (SRMP).
Unlike reliable sessions, the source and destination do not have to be
running at the same time. This implicitly enables scenarios where queues
are, in effect, used as a load-leveling mechanism when there is a mismatch
between the rate of message production by the source and the rate of the
message consumption by the destination
Queues in WCF provide both reliable
transfers of messages and separation between sources and destinations at the
cost of high latency.
· Durable
Messages
A durable message is one that is never lost due to a disruption in the communication. The messages in a durable message pattern are always saved to a database. If a disruption occurs, the database allows you to resume the message exchange when the connection is restored.
A durable message is one that is never lost due to a disruption in the communication. The messages in a durable message pattern are always saved to a database. If a disruption occurs, the database allows you to resume the message exchange when the connection is restored.
· Transactions
WCF also supports transactions using one of three transaction models: WS-AtomicTtransactions, the APIs in the System.Transactions namespace, and Microsoft Distributed Transaction Coordinator
WCF also supports transactions using one of three transaction models: WS-AtomicTtransactions, the APIs in the System.Transactions namespace, and Microsoft Distributed Transaction Coordinator
· AJAX and REST Support
REST is an example of an evolving Web 2.0 technology. WCF can be configured to process "plain" XML data that is not wrapped in a SOAP envelope. WCF can also be extended to support specific XML formats, such as ATOM (a popular RSS standard), and even non-XML formats, such as JavaScript Object Notation (JSON).
REST is an example of an evolving Web 2.0 technology. WCF can be configured to process "plain" XML data that is not wrapped in a SOAP envelope. WCF can also be extended to support specific XML formats, such as ATOM (a popular RSS standard), and even non-XML formats, such as JavaScript Object Notation (JSON).
· Extensibility
The WCF architecture has a number of extensibility points. If extra capability is required, there are a number of entry points that allow you to customize the behavior of a service.
The WCF architecture has a number of extensibility points. If extra capability is required, there are a number of entry points that allow you to customize the behavior of a service.
Difference between Web Service in ASP.NET & WCF Service
WCF is a replacement for all earlier web service
technologies from Microsoft. One will get a much higher degree of flexibility
and portability doing things in WCF than through traditional ASMX, because WCF
is designed, from the ground up, to summarize all of the different distributed
programming infrastructures offered by Microsoft.
|
Features
|
Web
Service
|
WCF
|
|
Hosting
|
It can be hosted in IIS
|
It can be hosted in IIS, windows
activation service, Self-hosting, Windows service
|
|
Programming
|
[WebService] attribute has to be
added to the class
|
[ServiceContraact] attribute has
to be added to the class
|
|
Model
|
[WebMethod] attribute represents
the method exposed to client
|
[OperationContract] attribute
represents the method exposed to client
|
|
Operation
|
One-way, Request- Response are the
different operations supported in web service
|
One-Way, Request-Response, Duplex
are different type of operations supported in WCF
|
|
XML
|
System.Xml.serialization name
space is used for serialization
|
System.Runtime.Serialization
namespace is used for serialization
|
|
Encoding
|
XML 1.0, MTOM(Message Transmission
Optimization Mechanism), DIME, Custom
|
XML 1.0, MTOM, Binary, Custom
|
|
Transports
|
Can be accessed through HTTP, TCP,
Custom
|
Can be accessed through HTTP, TCP,
Named pipes, MSMQ,P2P, Custom
|
|
Protocols
|
Security
|
Security, Reliable messaging,
Transactions
|
An endpoint in WCF can be communicated with just as easily
over SOAP/XML as it can over TCP/binary and to change this medium is simply a
configuration file mod. In theory, this reduces the amount of new code needed
when porting or changing business needs, targets, etc.
Web Services can be accessed only over HTTP & it works
in stateless environment, where WCF is flexible because its services can be
hosted in different types of applications. Common scenarios for hosting WCF
services are IIS,WAS, Self-hosting, Managed Windows Service.
The major difference between them is that Web Services Use
XmlSerializer.
But WCF Uses DataContractSerializer which is better in Performance as compared to XmlSerializer.Why to prefer DataContractSerializer over XmlSerializer:
- Only
Publicfields or Properties of .NET types can be translated into XML - Only the
classes which implement
IEnumerable - Classes
that implement the
IDictionary
Difference between DataContractSerializer and XMLSerializer
- A
practical benefit of the design of the
DataContractSerializerXmlserializer. - XML
Serialization does not indicate which fields or properties of the type are
serialized into XML whereas
DataCotractSerializer - Explicitly shows the which fields or properties are serialized into XML
- The
DataContractSerializerHashTable
Client Development
Clients for the ASP.NET Web services are generated using the command-line tool WSDL.EXE.WCF uses the
ServiceMetadata tool (svcutil.exe) to generate the client for the service. Exception Handling
In ASP.NET Web services, unhandled exceptions are returned to the client as SOAP faults.In WCF Services, unhandled exceptions are not returned to clients as SOAP faults. A configuration setting is provided to have the unhandled exceptions returned to clients for the purpose of debugging.
Performance impact caused by loading the ServiceModel HttpModule
In the .NET Framework 3.0, the WCF HttpModule
was installed in the root Web.config file such that every ASP.NET application
was WCF enabled. This might affect performance, so one can remove ServiceModel
for the Web.config file if not needed as shown in the following example.
<httpModules>
<remove
name=”ServiceModel” />
<httpModules/>
References:
No comments:
Post a Comment